The invention relates generally to communications cable, cabling, and cordage, and more particularly, to twisted pair cabling with jackets surrounding a cable core.
Communication cables typically include a number of insulated wires therein. In order to minimize the problem of interference and random noise between the wires, the wires in the cable are generally twisted in pairs. At least one type of high-speed data communications cable includes a core having a filler material, a number of twisted pairs arranged around the filler material, and an insulative jacket surrounding the core. The twisted pairs are arranged in a manner to optimize performance in terms of impedance, attenuation, skew, and cross talk, among other things, for high-speed data and communication networks.
Certain types of cable have been found to meet frequency response specifications when tested at certain frequencies, according to, for example, the Telecommunications Industry Association and Electronics Industry Association category 5 and category 6 standards. When installed, however, the cables have not proven to consistently perform to their design standards. It is believed that manipulation and handling of the cable during manufacturing, distribution and installation sometimes causes relative movement between the cable jacket and the cable core. Relative movement of the cable jacket and the core can negatively impact cable performance, including, among other things, the “headroom” of the cable, or the differential between the frequency response of the cable at a test frequency and the maximum limit of the cable design. Thus, as the headroom is reduced, the ability of the cable to perform at higher frequencies is compromised. In the midst of increasing frequencies used in modern telecommunications and computer applications, the headroom of the cabling used in such a system is becoming increasingly important.
Some twisted pair cables are known to include separate compartments for each twisted pair in the cable. The compartments are formed through either the configuration of the jacket or with a separator structure encased by the jacket to prevent movement of the twisted pairs and to prevent crosstalk between the twisted pairs. See for example, U.S. Pat. Nos. 4,777,325 and 6,284,954. The jacket configurations and/or the separation structures, however, add additional cost and complexity to the cable, and can reduce the flexibility of the cable and hence make it more difficult to install. It would be desirable to preserve the headroom of a cable design for maximum performance of the cable in the field at a lower cost and without adversely affecting the flexibility of the cable.